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module: postpone lt_dlclose() until a safe time

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When unloading a module, lt_dlclose() may remove the module from memory.
If a module unloads itself, it's not safe to call lt_dlclose()
synchronously from pa_module_unload(), because the execution may return
to the module code that was removed from memory. To avoid this
situation, let's postpone lt_dlclose() until it's safe to call it.

BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=96831
This commit is contained in:
Tanu Kaskinen 2016-09-21 12:55:08 +03:00
parent c81f3da53b
commit 509cfd9138
1 changed files with 15 additions and 1 deletions
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16
src/pulsecore/module.c
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@ -228,6 +228,12 @@ fail:
return NULL; return NULL;
} }
static void postponed_dlclose(pa_mainloop_api *api, void *userdata) {
lt_dlhandle dl = userdata;
lt_dlclose(dl);
}
static void pa_module_free(pa_module *m) { static void pa_module_free(pa_module *m) {
pa_assert(m); pa_assert(m);
pa_assert(m->core); pa_assert(m->core);
@ -246,7 +252,15 @@ static void pa_module_free(pa_module *m) {
if (m->proplist) if (m->proplist)
pa_proplist_free(m->proplist); pa_proplist_free(m->proplist);
lt_dlclose(m->dl); /* If a module unloads itself with pa_module_unload(), we can't call
* lt_dlclose() here, because otherwise pa_module_unload() may return to a
* code location that has been removed from memory. Therefore, let's
* postpone the lt_dlclose() call a bit.
*
* Apparently lt_dlclose() doesn't always remove the module from memory,
* but it can happen, as can be seen here:
* https://bugs.freedesktop.org/show_bug.cgi?id=96831 */
pa_mainloop_api_once(m->core->mainloop, postponed_dlclose, m->dl);
pa_hashmap_remove(m->core->modules_pending_unload, m); pa_hashmap_remove(m->core->modules_pending_unload, m);